Overexpression and characterization of a novel GH4 galactosidase with β-galactosidase activity from Bacillus velezensis SW5

A novel galactosidase gene (gal3149) was identified from Bacillus velezensis SW5 and heterologously expressed in Escherichia coli BL21 (DE3). The galactosidase, Gal3149, encoded by gal3149 an open reading frame of 1,299 bp, 433 amino acids length. Protein sequence analysis showed that Gal3149 belonged to family 4 glycoside hydrolases (GH4). displayed higher enzyme activity for the substrate 2-nitrophenyl-β-d-galactopyranoside (oNPG) than 4-nitrophenyl-α-d-galactopyranoside (pNPαG). This is first time belonging GH4 has been shown exhibit β-galactosidase activity. optimal at pH 8.0 50°C, exhibited excellent thermal stability, with retention 50% relative after incubation a temperature range 0 50°C 48 h. significantly improved K+ Na+, strongly or completely inhibited Ag+, Zn2+, Tween-80, Cu2+, carboxymethyl cellulose, oleic acid. rate hydrolyzed lactose 1 mL milk U reached about These properties lay solid foundation application lactose-reduced dairy industry.